<!DOCTYPE html>
<html lang="en">
    <head>
        <title></title>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1">
    </head>
    <body>
        <script>
            var array = [1,2,3];
            delete array[1]         // 移除2
            alert(array)            // 打印 1,,3
            alert(array.length)     // 长度为3
            array.forEach(alert)    //只会谈出1,3
        </script>
    </body>
</html>